This invention relates to a multicolor transfer heat-sensitive recording apparatus which records data in multicolor according to a transfer type heat-sensitive recording system.
In the transfer type heat-sensitive recording system, a recording sheet or ordinary paper is laid on an ink donor sheet or thermally recording medium, and a thermal pulse is applied to the ink donor sheet. A layer of ink, which is fluidized or sublimated when heated, is formed on the ink donor sheet. Therefore, the ink in the part of the ink donor sheet where the thermal pulse is applied is transferred onto the recording sheet, so that the image data is recorded thereon. Accordingly, in the recording system, multicolor recording can be carried out with a plurality of recording stations arranged along the recording sheet conveying path.
FIG. 1 shows the principle of conveying an ink donor sheet and a recording sheet in a recording station. The recording sheet 1 is moved in the direction of the arrow along a conveying path 2 indicated by the dotted line, and a sensor (not shown) detects when the front edge of the recording sheet 1 comes near a thermal head 3, to start an electric motor 4. A back roller 5 is confronted with the thermal head 3. The torque of the motor 4 is transmitted to the back roller 5 through a belt 6 and a pulley 7 coupled directly to the rotary shaft of the back roller 5. As the back roller 5 is turned, the ink donor sheet 9 supplied from a supply roll 8 is conveyed in the direction of the arrow while being pressed against the thermal head 3, so as to be wound on a take-up roll 11. In this operation, the recording sheet 1 is conveyed in the same direction while being held between the ink donor sheet 9 and the cylindrical surface of the back roller 5.
In the recording system, the ink donor sheet and the recording sheet are conveyed by a feed roller such as a back roller for conveying a recording sheet and other components such as for instance a motor for driving the feed roller. Therefore, if the components of the recording stations in the entire recording apparatus are different in dimension or electrical characteristic from one another, then the amounts of auxiliary scanning per line of a recording sheet in these recording stations become different from one another. Accordingly, the accumulation of the differences results in a color shift. The occurrence of accumulated error of the drive source, namely, the motor may be prevented by employment of a stepping motor. On the other hand, if the feed rollers such as back rollers are slightly different in diameter from one another, the differences are accumulated as the rollers turn.
In a conventional multicolor transfer heat-sensitive recording apparatus, in order to prevent the occurrence of color shift due to the accumulation of such differences, the force of depression between the thermal head and the back roller is adjusted for instance, so that the diameter of the roller is substantially varied. However, such mechanical adjustment can be achieved only by a skilled person. In addition, sometimes the force of depression of the ink donor sheet against the thermal head is unsuitable for recording; that is, the ink transferring characteristic is lowered.